As mentioned previously, name servers in an administrative domain maintain the DNS database. They also run the in.named daemon, which implements DNS services. in.named is a public domain TCP/IP program and is included with the Solaris operating environment.
The in.named daemon is also called the Berkeley Internet Name Domain service, or BIND, because it was developed at the University of California at Berkeley.
Each domain must have one master server and should have at least one slave server to provide backup. Implementing DNS explains primary and secondary servers in detail.